Transplantations of cultured tissue are used to a large extent. For example, skin wounds or skin disorders may make it necessary to carry out skin transplantation. To this end, it is possible to remove a skin transplant at one body site and to transplant it to another body site. However, such techniques may be unsatisfactory especially when there are relatively extensive skin wounds or skin disorders. Examples of such skin lesions can include burns with skin injuries that are extensive and deep, large birthmarks or chronic wounds.
To avoid such problems, it is possible to use cultured skin in order to treat the skin lesions. Skin cells can be removed in a biopsy and applied to a matrix or embedded in said matrix. In the matrix, the skin cells can grow to form dermis and epidermis. In this way, it is possible to culture so-called skin grafts. Other techniques for carrying out “tissue engineering”, by means of which material can be generated for skin transplantation, can be used. Exemplary techniques for generating skin substitutes by “tissue engineering” are, for example, described in T. Biedermann et al., “Tissue engineering of skin for wound coverage.” European Journal of Pediatric Surgery, 23(05): 375-382 (2013); L. Pontiggia et al., “Optimizing in vitro culture conditions leads to a significantly shorter production time of human dermo-epidermal skin substitutes”. Pediatric Surgery International, 29(3): 249-256 (2013); or D. Marino et al., “Bioengineering dermo-epidermal skin grafts with blood and lymphatic capillaries”. Science Translational Medicine, 6(221): 221ra14 (2014).
One challenge in the use of cultured skin or other techniques for producing skin substitutes is checking the material as to whether it is suitable for use in the transplantation. The suitability of the material for use in the skin transplantation depends, for example, on the number of cells and/or on a ratio of the cell number of different cell types. Furthermore, the suitability of the material for use in the skin transplantation can also depend on whether and to what extent cells are functionally impaired, for example by apoptosis or necrosis.
There are similar challenges in the use of other cultured tissues as transplant, such as, for example, cartilage substitute or bone substitute.
To check the material for its suitability for use in the transplantation, it is, for example, possible for a sorting of the fully cultured cell populations by means of flow cytometry before the introduction into the matrix. The so-called “DNA count” method is used in order to count the number of total cells in the fully cultured matrix. However, such techniques are expensive and time-consuming. Depending on the implementation, such techniques may also involve a partial destruction of the material to be tested for its suitability for use as transplant. Furthermore, such techniques also only provide limited information or do not provide any information about the functionality and/or quality of the cells.
Moreover, when carrying out the flow cytometry, it is necessary to culture a large number of cells beforehand in order to allow the measurement. This is time-consuming and cost-intensive (e.g., in the case of fluorescence labeling via antibody-based labels). The cells are no longer available to the patient. The flow cytometry does not provide any information about the final cell count, the ratio of the number of different cell types and/or the quality of the cells in a transplant cultured to completion.
“DNA count” methods can be set up on a portion of the transplant, but do not provide any information about the cell types and/or the ratio of different cell types.